In order to enlarge the coverage of communication systems and to increase capacity of systems, one or more relay stations (Relay Station, shortened as RS) may be set between a multi-hop relay base station (Multi-hop Relay Base Station, shortened as MR-BS) and mobile stations (Mobile Stations, shortened as MS). Channel resource allocation must be implemented by an MR-BS in a centralized relay system, therefore the design of a hybrid automatic repeat request (Hybrid Automatic Repeat Request, shortened as HARQ) of the relay system that schedules a RS in a centralized manner is relatively complex.
The form of an HARQ will be increased accordingly due to the introduction of an RS, and the typical forms are an end-to-end HARQ and an hop-by-hop HARQ. With regard to the end-to-end HARQ of the centralized relay, an uplink control station has allocated a corresponding feedback channel for each RS to transfer an ACK/NACK before the RS transmits a certain HARQ burst (also called sub-burst). In existing technologies, the RS knows the feedback channel allocated to itself by calculation after receiving the burst which is to be transferred, and then transmits feedback over corresponding resource. Once the burst fails to be transferred by the relay, a delay for retransmission may also become large due to the long feedback time because air interface resource must be allocated by the MR-BS when centralized scheduling is adopted.
Moreover, as shown in FIG. 1, when one RS applies access to multiple MSs, one relay tunnel can be set up between the access RS and the MR-BS. Protocol data units (shortened as PDUs) of multiple MSs can make up one tunnel burst by the MR-BS to act as a basic unit of the HARQ to be transmitted in one frame. After the tunnel burst reaches the access RS successfully, the RS restores the PDUs of each MS, and continues to accomplish the HARQ on the access link.
Presently, in the IEEE802.16j standard draft, the tunnel data can be divided into two modes: a tunnel packet mode and a tunnel burst mode. In the tunnel packet mode, the PDU of each MS is assembled as one tunnel packet to be transmitted. The tunnel packet has its own packet header (including a Tunnel Connection Identifier (Tunnel CID, shortened as TCID)) and a Cyclic Redundancy Check (Cyclic Redundancy Check, shortened as CRC) code. One burst may have tunnel packets on different tunnels. In the tunnel burst mode, the TCID is provided in a downlink map information element (DL MAP IE), therefore the tunnel data may be taken as one burst of a physical layer. One burst can only include PDUs of MSs on the same tunnel. A reduced connection identifier (RCID) of each PDU is replaced by the same TCID.
However, an HARQ method completely involving tunnel data transmission is never prescribed in existing technologies. For example, an ACK of each MS cannot be transferred on a tunnel individually when a tunnel packet or a tunnel burst is used for transmission. The advantage of tunnel transmission may be lost if a TCID is not added to tunnel data while a data burst of each MS is fed back individually, because at this moment, it may seem that multiple MSs perform the HARQ independently.